As long as it is easily customizable, has great features and secure...many CMS' fail because of security issues.
Also for it to become widely used, it has to be extensibly marketed due to the wide proliferation of CMS' like Wordpress, Drupal. What will your CMS bring to the market? More features than Wordpress? Better security? Will it serve a niche market? ...
But if it's just for learning purposes, a CMS is a great starting place.